Backgrounds: Myocardial contrast echocardiography (MCE) provides the potential for real time, noninvasive assessment of myocardial perfusion. The purpose of this study was to investigate clinical usefulness of MCE for predicting myocardial viability in acute myocardial infarction (AMI) patients. Materials and Methods: We investigated 46 patients with AMI after primary percutaneous coronary intervention (PCI). 2D-echocardiography and MCE were performed to assess regional wall motion abnormality (RWMA) and myocardial perfusion defects within 24 hours after primary PCI. By using MCE, the quantitative MCE parameters were measured: A, representing myocardial blood volume; 棺, representing the mean micro-bubble velocity; and A 棺, representing myocardial blood flow (MBF). We performed follow-up echocardiography after 1 year. Results: Of 46 patients, 14 patients had a significant perfusion defect (group A) and 32 patients had no perfusion defect or preserved perfusion defect by MCE (group B). However, there was no difference between two groups with quantitative MCE parameters (A; 6.12짹3.21 vs. 5.44짹1.58, p=0.456, 棺; 0.26짹0.22 vs. 0.17짹0.13, p=0.185, MBF; 1.51짹1.83 vs. 0.9짹0.64, p=0.238, respectively). On the follow-up echocardiography, group B showed significant improvement of wall motion abnormality (94.1% vs. 42.9%, p=0.014). The sensitivity and specificity of MCE for wall motion was 80% and 84.2%, respectively. Conclusion: Real time MCE may be a useful noninvasive diagnostic tool to predicting myocardial viability after primary PCI in patients with AMI. Further large clinical trials are needed. Key Words : Myocardial contrast echocardiography, perfusion defect, myocardial infarction